MEXICAN CALENDAR. 127 
The carved stone represented in the plate was found in the year 1790, 
about six feet below the surface of the Plaza, in the city of Mexico. The 
opinion of the best antiquarians is, that it was the Tonalponalli,- -or " solar 
reckoning " of the ancient Mexicans, derived by them probably from the 
Toltecs. 
Before describing this relic, I will present a brief account of the 
division of time among these nations, illustrating in this manner and by 
the stone itself, one branch of the arts and sciences, at least, in which 
they had made a great and civilized progress. 
The Mexicans had two Calendars by which they computed Time ; the 
first being used for the " reckoning of the moon," and the regulation of 
their religious festivals, and the other for the " reckoning of the sun," or 
civil purposes. 
Their civil year consisted of 18 months of 20 days each, by which 
division they gave the year 360 days; but the remaining five days were 
added to the last month, and bore the name of nemontemi, or " useless 
days." 
The tropical year being six hours longer than 365 days, they lost a 
day every four years ; but this fact appears to have been entirely disre- 
garded by them in their calculations, until the expiration of their cycle 
of 52 years ; when, having lost, in all, 13 days, they added that number 
to the period, before they commenced another cycle. 
The 18 months had each a name derived from some festival, bird, 
plant, or fruit, occurring or appearing at that season, which name was 
designated by a peculiar hieroglyphic. The 20 days of the month had 
also each a name and mark, that was ever the same in all the eighteen. 
They reckoned by cycles of 52 years ; and subdivided the months into 
four periods, or weeks of five days ; each day of which commenced, 
as among the Romans and other nations, at sunrise, and was separated 
into eight portions.* 
The stone (of which I have presented an extremely accurate drawing 
from one made v/ith the greatest care by De Gama,) is now walled against 
the base of one of the towers of the Cathedral, where it passes by the. 
name of el Relax de Montezuma, or " Montezuma's watch." It is a vast 
mass of basalt, eleven feet eight inches in diameter, and the circular portion 
is raised by a rim of about 7| inches from the broken square of basalt, 
out of which the whole was originally carved. This rim is adorned with 
the sculpture represented in the second figure. 
De Gama, in his '' Descripcion Historica,'' has prepared a long and 
very learned account of the various figures and symbols with which this 
Calendar is covered, and from his observations, and those of Nebel, I have 
* McCulloh's Res ■ 201, et seq. 
